This disclosure pertains to a reduced dark current Barrier-type photo detector that is comprised of a first semiconductor layer, a barrier, and a second semiconductor layer where at least one of the semiconductor layers is used for photo-absorption and the effective conduction and valance band alignments for the two layers and Barrier are arranged so as to allow photo-generated minority carrier flow but filter or block majority carrier flow. Individual elements in the photo detector array may be defined by isolating active regions in the first or second layer such that these regions form the pixels. The Barrier, however, may be preserved such that it extends beyond the extent of the isolated pixel areas. Although applicable to a wide range of barrier-type photodetectors, the exemplary embodiments and associated energy band diagrams presented in this disclosure depict an nBn Barrier type photodetector. The structures and methods discussed herein, however apply as well to nBn, pBp, nBp and pBn structures.
An embodiment of an exemplary nBn structure electron band diagram is illustrated in FIG. 1. The embodiment represents an embodiment of the concepts described in U.S. patent application Ser. No. 11/276,962. The underlying concept relates to driving minority carriers from a photo absorbing layer 1000 to a contact region 1020 through a Barrier 1010 where the compositions of the absorber, barrier, and contact layers are such that minority carriers can penetrate the Barrier 1010 but majority carriers cannot. As can be seen in FIG. 2 and as discussed in U.S. patent application Ser. No. 11/276,962, the pixels in the contact layer 2030 are isolated by etching down to, but not through, the Barrier 2010 in order to accomplish pixel delineation. In the embodiment shown, each pixel is associated with an ohmic contact 2040 and a read-out interconnect point 2080. Minority carriers generated in the absorber layer 2000 pass through the Barrier 2010 and into the contact layer 2030 where they are read-out through the interconnect 2080 via the ohmic contact 2040.
It would be an improvement in terms of manufacturability, reliability, versatility and production yield to delineate and isolate pixels in such a photo-detector in ways other than material removal.